Some display devices require a backlight unit to generate light in order to display an image. The backlight unit supplies the light to a display panel including liquid crystal. The backlight unit includes a light emitting device and units to effectively transfer light output from the light emitting device toward the liquid crystal.
Light emitting diodes (LEDs) may be employed as a light source of the display device. Further, in order to effectively transfer the light output from the light source toward the display panel, a light guide plate and an optical sheet may be stacked and used.
In this case, optical members, which convert the wavelength of the light generated from the light source so that white light may be incident into the light guide plate or the display panel, are applicable to the display device. In particular, in order to convert the wavelength of the light, quantum dos may be used.
The quantum dots have a particle size of 10 nm or less, and represent unique electro-optical characteristics according to the particle size. For example, when the quantum dot substantially has the particle size of 55 Å to 65 Å, 40 Å to 50 Å, or 20 Å to 35 Å, the quantum dot represents red-based colors, green-based colors, or blue-based colors, respectively. If the quantum dot represents a yellow color, the quantum dot may have an intermediate particle size between the particles sizes of the quantum dots representing a red color and a green color. As the spectrum according to the wavelength of light is changed from the red color to the blue color, the size of the quantum dot is sequentially changed from about 65 Å to about 20 Å. The numerical values may have error.
In order to form an optical member including quantum dots, a quantum dot representing RGB, which constitute the three primary colors of light, or RYGB may be formed through a spin coating process or a printing process for a transparent substrate including glass. In this case, if the optical member further includes quantum dots representing a yellow color (Y), white light closer to natural light may be obtained. A matrix (medium) that carries quantum dots by dispersing the quantum dots may include an inorganic material or polymer to emit visible light and UV-band light (including Far UV light) or to represent superior transmittance with respect to the visible-band light. For example, the above material may include inorganic silica, poly-methylmethacrylate (PMMA), polydimethylsiloxane (PDMS), poly lactic acid (PLA), silicon polymer, or YAG. In particular, the quantum dots and the medium may be denatured or damaged due to heat.
The display device to which the quantum dots are applied is disclosed in Korean Unexamined Patent Publication No. 10-2011-0012246.